1. Field of the Invention
This invention relates generally to semiconductor integrated circuit (IC) burn-in testing, and more particularly to a technique for enhancing observability of IC failures during burn-in tests.
2. Description of the Prior Art
Burn-in testing for a semiconductor integrated circuit (IC) device is carried out to eliminate weak devices that are most likely to fail during early life of the product. The test is performed within a burn-in oven by placing multiple devices on a burn-in board at typically a 125 degrees Centigrade (C) temperature and by applying a higher voltage than the normal operating voltage to the device. Due to these extreme stress conditions, weak devices may show failures. To detect these failures during the test itself, the device functionality can be monitored. Depending upon the complexity of the device, the burn-in board configuration and the burn-in oven, only a limited number of devices can be burned-in at the same time. In a complex device, there are several outputs that require monitoring. With limited pin monitoring capability of the oven, monitoring several pins of multiple devices on a board becomes very challenging. In most cases, there are only one or two device pins that can be monitored by the oven. Such limitations regarding observability prevent any substantial scope of fault isolation. On the other hand, observability of failures helps burn-in hardware/software debug during IC development. During the actual burn-in process, the monitoring signal capability helps in eliminating the failing device(s) and is also useful in generating failure statistics for a particular device or process.
In view of the foregoing, it would be both beneficial and advantageous to provide a technique to enhance observability of IC failures during burn-in tests beyond that presently known in the burn-in testing art while adhering to the limitations described herein before.